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This is the download page for the

Convolution approximation for swift Particles. (CasP)

CasP version 5.2 (January 2014),    ©2001-2014 freeware

The installation of this program requires

  • a) a windows operating system (W9X, W-ME, W-NT, W2000, W-XP, W-Vista, or W-7)
  • b) installed RAM of 6 MB
  • c) free disc space of 2 MB
  • d) a Pentium or equivalent processor with a clock rate of > 1 GHz is recommended, especially for calculations involving heavy target atoms.

The CasP program is freeware. It may be copied and distributed only along with all the additional resource files of this package and only without fee. There is no restriction on the number of copies and on the recipients. Any publications, however, that make use of UCA or PCA results or other results of this program should be accompanied by proper references to the original work.

Energy Transfers and Stopping Power

In CasP fast numerical calculations of the mean electronic energy transfer Q_e (due to excitation and ionization of target atoms) are performed for each individual impact parameter b in a collision. The total electronic energy-loss cross-section S_e (equivalent to the stopping power) is subsequently calculated from Q_e(b). The computation of Q_e and S_e accounts for a selected predefined projectile-screening function. By selecting a proper screening function, it is possible to treat non-equilibrium energy-loss phenomena. Furthermore, the unitary convolution approximation UCA (default selection) is a non-linear theory, as it includes the Bloch terms. Therefore, even for bare projectiles, the results do not scale with the square of the projectile charge (as most other quantum theories do).


Detailed information on the present PCA and UCA models may be found in the online help text and in several publications listed therein. One recent example is

G. Schiwietz and P.L. Grande, "Introducing electron capture into the unitary-convolution-approximation energy-loss theory at low velocities", Physical Review A 84, 052703 (2011)

Please cite the latest references, e.g., the above mentioned paper and give the type of model ("UCA" is the default value) and the screening function ("charge-state scan" is the default value), when using results of CasP. Additional information and references to subsequent publications may be obtained from the on-line help system and the file "ReadMe.txt", supplied with CasP.

Download CasP now

  • a) Store the file caspxx.zip (file size: 1400 kByte) in a separate directory.
  • b) Extract/Unzip the contents (file sizes: about 2 MByte).
  • c) Check the ReadMe file for recent information.
  • d) Simply start the program "casp.exe".

Please use the on-line help system (help button) to get in touch with the program. Should you need additional information, please read the publications on the model (citations are found in the help files).

Please keep in mind:
It is not allowed to modify the program, to disassemble the program (casp.exe), or to change the CasP resource files (dens.dat and help files).